This invention relates to the use of a combination of selected zirconium and cerium salts in residual fuel oil to reduce the amount of particulate matter formed during combustion.
Residual fuel oils, including Grades Nos. 4, 5 and 6 (ASTM D-396), are widely used in a variety of industrial heating and steam boiler applications. A particularly desired fuel oil is No. 6, which is extensively used by utility and power companies.
State and federal EPA emission standards are currently limiting the use of residual fuels which produce excessive amounts of particulate emission during combustion and thus are not in compliance with standards.
However, the situation is relatively complicated, since state-to-state emission standards tend to be different and compliance by a residual fuel oil in one state may not necessarily be achieved in another, and further, since standards are continuously subject to change, a fuel oil currently in compliance may not be in compliance in the near future in the same location and under the same end-use conditions.
Fuels which tend to produce excessive amounts of particulate emissions generally have one or more characteristics associated with them: a sulfur content above about 1 percent; a Conradson Carbon Residue (ASTM D-189, also termed "Con Carbon" in the art) above about 7 percent; or a high asphaltene content. Fuels yielding particulate emissions that surpass the existing standards can't be directly used, but in some cases can be blended in admixture with fuels that do meet existing standards which are generally low in sulfur and/or low in "Con Carbon" and asphaltene content. This situation has resulted in an overall increased demand for fuel oils which meet emission standards despite their diminishing supply and attendant increase in cost.
What is desired is a technique for increasing the utility of these high emission yielding residual fuel oils for industrial heating purposes in a manner that results in acceptable particulate emissions, despite a high sulfur content, a high Con Carbon Residue and/or high asphaltene content.
In the area of related problems, it is known in the art that the use of specific additives in certain hydrocarbon fuels, can reduce smoke or soot upon combustion in certain instances. It is also known to use specific additives in fuels to inhibit corrosion, inhibit slag formation in boilers and reduce the deleterious effect of vanadium present in such fuels.
It has recently been shown that zirconium salts of selected carboxylic acids have a beneficial effect on residual fuel oil in reducing the particulate matter formed during combustion.